Effects of hydrazine addition on gas evolution and performance of the direct borohydride fuel cell

A fuel cell configuration using alkaline NaBH4-N2H4 solutions as the fuel is suggested. Gas evolution behaviors and cell performances of alkaline NaBH4-N2H4 solutions on different catalysts have been studied. It is found that gas evolution behaviors are influenced by the applied anodic catalysts and the concentration of NaBH4 and N2H4. NaBH4 is mainly electro-oxidized on Pd but N2H4 is mainly electro-oxidized on Ni and surface-treated Zr-Ni alloy when using NaBH4-N2H4 solutions as the fuel and a composite of Pd, Ni and surface-treated Zr-Ni alloy as the anodic catalyst. The cyclic voltammetry results show that electrochemical oxidation potential of NaBH4 is higher than that of N2H4. Adding hydrazine into alkaline sodium borohydride solutions can suppress gas evolution and improve the cell performance of the DBFC. The performances of fuel cells using NaBH4-N2H4 solutions are comparable to that of fuel cell using N2H4 solution.